There are growing needs for analyzing the structure and characteristics of substances not in vacuum but in a gas atmosphere and for performing in-situ observation of the synthetic process of the substances in the gas atmosphere with use of transmission electron microscopes (TEMs), scanning transmission electron microscopes (STEMs) and the like.
For observation in the gas atmosphere, there is a method as disclosed in Patent Literature 1 and Patent Literature 2, in which a sample holder includes a mechanism for holding a sample between two grids and introducing and exhausting gas into and from a space between the grids. There is another method as disclosed in Patent Literature 3 in which, in order to protect a diaphragm from pressure variations in the inside of a cell and to prevent gas diffusion, a sample is enclosed with a cell membrane and the membrane is provided with two holes which are covered with diaphragms so that an electron beam passes through the membrane. There is still another method as disclosed in Patent Literature 4 in which a sample holder has a dual-stage cell structure for preventing gas diffusion in the case where a diaphragms is damaged, the dual-stage cell structure having another diaphragms placed outside the cell formed from the diaphragms.